Aromatic carboxylic acids having two carboxyl groups in one molecule and acid halides of these compounds are used as the material for aromatic polyamide resins, polyarylate resins, polybenzoxazole resins and polybenzothiazole resins. Resins having various structures are produced and used in accordance with the applications.
In general, these resins have excellent heat resistance although these resins are thermoplastic macromolecular compounds and these resins are frequently used for applications exposed to high temperatures. As the means of further enhancing the heat resistance, introduction of thermosetting substituents has been attempted. Therefore, a material used for such resins has been desired.